Cell phones depend on both mechanical and electromagnetic waves to be useful. which answer below correctly identifies how each wave is used in cell phones?

a. mechanical waves allow the buttons to be pressed to make a call; electromagnetic waves allow a signal to be picked up when making a call

b. mechanical waves light up the screen; electromagnetic waves create the sound when the phone is ringing

c. mechanical waves allow the cell phone to emit a sound when ringing; electromagnetic waves allow a signal to be picked up when making a call.

d. mechanical waves allow a signal to be picked up when making a call; electromagnetic waves allow the cell phone to emit a sound when ringing

The answer is: C. Mechanical waves allow the cell phone to emit a sound when ringing; Electromagnetic waves allow a signal to be picked up when making a call.

Mechanical wave transfers energy through a medium and electromagnetic waves require no medium, but can travel through one.

There are three types of mechanical waves: transverse waves, longitudinal waves (sound) and surface waves.

Cell phones operate with radio frequencies.

Radio waves are the electromagnetic waves with the longest wavelengths (1dm to 100 km), lowest frequencies (3kHz to 3GHz) and lowest energy (124 peV to 12,4 μeV).

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water pollution kills aquatic life. aquatic life includes algae and other plant life that use photosynthesis. photosynthesis takes   c02 out of the air.  

c02is a greenhouse gas.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm